The aim of the proposed research is to determine the molecular mechanism by which lactose induces the enzyme Beta-galactosidase in the yeast Kluyveromyces lactis. We are using this system as a simple model system for studying genetic regulation in a eucaryote. Our experimental approach is to probe the mechanism of induction in the wild type organism, to isolate lac and regulatory mutants, to characterize the mutants by genetic and biochemical techniques, and to compare the induction process in mutant and wild type. We will determine whether induction is regulated at the level of transcription or translation by examining whether Beta-galactosidase or its mRNA are synthesized de novo after induction. We will isolate the yeast gene coding for Beta-galactosidase using recombinant DNA techniques. The mechanism for regulating expression of this gene will be examined in vitro using purified cell components.